Genetically modified mice are important tools for studying kidney physiology and diseases. However, expertise and equipment for physiological analysis of kidney function in mice are not readily available to many investigators in the renal research community. Furthermore, production of mutant mice has allowed many investigators outside the renal community to uncover unexpected renal phenotypes and enter into renal research. The objective of the Physiology Core is to assist center investigators with a wide range of physiological techniques to study kidney physiology and diseases at the cellular, organ, and whole animal level. To achieve these objectives, the Core will provide the following specific services: (1) Whole animal clearance studies; (2) Measurements of serum and urine electrolytes and chemistry; (3) Measurement of blood pressure; (4) Measurement of electrolytes in nl volume using ion-selective electrode (5) Isolation of individual tubules for real-time PCR and immuno-fluorescent staining; (6) In vitro microperfusion of individually isolated tubules; (7) Electrophysiological studies. Procedures will be in place to evaluate efficiency and to maintain appropriate quality control of the services that are provided. The Core will also provide education and training to the staffs of center investigators. The core directors have a track record of providing assistance and training to visiting scientists locally and nationally. The Core director. Dr. Chou- Long Huang, received his PhD in Physiology from UCSF working with Dr. Floyd Rector on renal physiology and completed postdoctoral training with Dr. Lily Jan at UCSF working on K+ channels. He is well recognized for his studies of renal ion channels. His laboratory actively employs electrophysiological and other physiological approaches and mouse models. The co-director. Dr. Michel Baum, also trained in Dr. Floyd Rector's lab in UCSF. Throughout his independent research career, he has studied renal ion transport using in vitro microperfusion and microanalytic and imaging techniques on individually isolated tubules. The Physiology Core will be housed in the laboratories of the core directors in the Departments of Internal Medicine and Pediatrics at UTSW.